mitchell



E. H. MITCHELL.

AIRSHIP 0F RIGID TYPE.

APPLICATION FILED APR. 23. I519.

Patented Aug. 26, 1919.

3 SHEETS-SHEET E. H. MITCHELL.

AIRSHIP oF'fl mom TYPE.

APPLICATION FILED APR. 23.1919.

1 3 1 4,349 I Patented Aug. 26, 19191 3 SHEETSSHEET 2.

E. H. MITCHELL.

AIRSHIP OF RIGID TYPE.

aryucmou FILED APR. 23. 1am

1,3 1 4,349 I Patented Aug. 26, 191$).

K 3 SHEETSSHEET 3.

UNITED STATES PATENT OFFICE.

EWEN HENDERSON MITCHELL, OF IBEDFORD, ENGLAND, ASSIG-NOR OF ONE-T31R15 T0 ALBERT EUSTACE SHORT AND ONE-THIRD TO HUGH OSW'ALD SHORT, BOTH 0F BEDFORD, ENGLAND.

AIRSHIP OF RIGID TYPE.

Specification of Letters Patent.

Patented Aug. 26, 1919.

To all whom it may concern Be it known that I, EWEN HENDERSON MITCHELL, a subject of the King of Great Britain, residing at Bedford, Bedfordshire, England, have invented certain new and useful Improvements in Airships of Rigid Type, of which the following is a specification.

This invention relates to balloons or airships of rigid type, the object being to construct same in such form and manner that I the structure is better adapted than heretofore to withstand the stresses due to the gas pressure, and consequently the structure can be made of the necessary strength while the weight can be decreased, advantages which will be obvious.

As at present constructed what is known as a rigid airship is generally circular or of slightly oval formation in transverse section, with the result that since the difference between the internal and external pressures varies from a very small pressure at the lowest point to a maximum pressure at the highest point, consequently the resulting tension in the fabric, circumferential wires or supporting rings, will vary, being greater at the top of the section and very small at the bottom and therefore bending moments and distorting stresses are introduced in the supporting structure which is usually partly counterbalanced by the tension of radial wires.

According to this invention the structure of the airship is made, in cross section, of a form such as hereafter described, so that in the average condition of pressure in the gas bags, the circumferential tension in the fabric, in the circumferential supporting wires and in the frames, Will be constant, thus obviating the necessity for employment of most of the radial wires and reducing the pressure on the longitudinal members and the bending moments in the frames.

In describing the present invention it is first to be explained that a primary or elementary form of transverse section has been selected, necessary for constant tension when the pressure at the low st p nt is eq al to atmospheric pressure, and such a form is shown in the outline diagram Figure' 1 of the accompanying drawings, being such that the radius of curvature varies inversely as the pressure. This form shown at Fig. 1 is that which would be assumed by a cyllndrical bag made of flexible material and open at the top, if filled with Water, the bag'having this form obviously being shown inverted in the diagram at Fig. 1.

Now the form shown at Fig. 1 would be unsuitable for the cross section of a rigid airship owing to the large ratio of height to breadth, and therefore according to this invention a plurality of forms similar to Fig. 1 are combined and the internal partitions which would result from such combination are removed.

The invention will be further described with reference to Figs. 2 and 3 of the accompanying drawings, Fig. 2 being a cross section of the airship sufficiently illustrating the same for the purposes of this specification, and Fig. 3 being a perspective view of a section of such an airship.

The gas container in transverse section'is of a shape composed by portions of three of the forms shown at Fi 1 conjoined, that is to say a laterally disposed portion 1 of the container conjoins at its upper part with a portion 2 of the upper part of such a form as is illustrated at Fig. 1, while the other laterally disposed portion 3 conjoins the opposite edge of the portion 2 and corresponds in shape to the portion 1, the sectional form of the gas container thus beingcomposed of conjoined segments producing an approximately pear-shaped fi re, hereafter referred to in this speci cation for the sake of brevity as pear-shaped the section so produced being such that the breadth and depth are sufiiciently nearly equal and the volume sufficiently approximates to that of a circular section of the same height.

It will now be-understood that the approximately pear-shaped transverse section referred to of the gas container has, exterfially at its upper part, two rentering gles hich extend. longitudin l y and are located at equal distances on opposite sides of the vertical central plane ofthe structure.

Such a gas container as described is constructed with closed ends as is well known, and several of such gas containersjare located end to end within the outer framework of the airship. The outer framework consists of longitudinal frames 4 connected by transverse frames 5, and the construction of longitudinal and transverse frames need not be specially described in this specification since they may be composed of lattice structures built up of light sheet metal, and the lower ends of the transverse frames 5 abut and are fixed to a corridor 6 forming the keel of the vessel.

The frame work is stiffened by diagonal tension wires 7 shown only in one bay as at Fig. 2' so as not to compllcate the drawing. The framework has a similarity to airships already constructed, excepting that at the upper part two of the longitudinal frames marked 8 and 9 are deeper to preserve the gas containers in the shape desired with the reentering angles as already described.

' The, external shape of the-complete structure is maintained so as to obviate reentering angles and so as to reduce surface friction, by an outer cover '10, see particularly Fig. 2.

Circumferential wires 11, Fig. 3, are secured at their lower ends only to thecorridor 6 where most of the weight is concentrated, the length of the wires 11 being such as to enable them to take up the shape shown,

that is to lie in contact with the inner faces of the longitudinal frames 4, and the said wires 11 are retained in position at each longitudinal frame by any suitable means, but are free to move circumferentially, thus insurin that no side strain is transmitted to the rames, and that the tension is equal throughout.

The upper end of each of the lift'wires '12, Fig. 2, is attached to one or other of the longitudinal girders 8, 9 of the framework, and the said wires 12 are taken through the gas bag at suitable points, say by conical 4 neck pleces or other known devices, and

their lower ends extend and are fixed to the lower part of the structure, that is to the corridor 6. The external shape of the structure is thus maintained in the longitudinal sense by the rigid framework-and the gas containers being of the form shown and described, the gas pressure produces practically no distorting stresses upon the rigid framework.

What I claim as my invention and desire to secure by Letters Patent is 1. A rigid airship comprisin a gas container of approximately pear-s aped figure in transverse section, the radius of curvature bein inversely proportional to the pressure, an in which the breadth and depth frames of sufliciently deep section to preserve the form of the said reentering angles of the said container.

2. A rigid airship comprisin ,a gas container of approximately pear-s aped figure in transverse section, and in which the breadth and depth are nearly equal, the upper part of said container having one or .more re'e'ntering angles which extend longitudinally of the container and are located at equal distances on opposite sides of the vertical central plane of the said container,v

in combination with an outer rigid framework composed of longitudinal and trans: verse frame members conforming to the gen- 'eral contour of said gas container and ing one or more of said longitudinal frames of sufliciently deep section to preserve the form of the said rente-ring angles of the said container, an outer cover extending externally around the said framework to preserve the external shape of the complete structure while obviating reentering angles and internal lift wires connected at their upper ends to the deep section frames at the reentering angles and at their lower ends connected to the base of the structure, the

said lift wires passing through the walls of the gas container.

3. A rlgid airship comprising a plurality of gas containers each of approximately pearshaped fi ure in transverse section having the brea th and depth nearly equal, the.

upper parts of said containers having one or more reentering angles which extend longitudinally of the containers and are located at equal distances on opposite sides of the vertical central plane of said containers, in combination with an outer rigid framework composed of longitudinal and transverse frame members conforming'to the gen- Y eral contour of said gas containers in transverse section, one or more of said longituv dinal frames of said framework being deeper than the other longitudinal frames to preserve the form ofthe reentering an les of said containers, a corridor for t e keel of the vessel to which the lower en s of said transverse frame members are fixed, circumferential wires secured at their lower ends only to said corridor, the len 11 of said wires being such as to enable 15 em to take up the form of the framework and containers in transverse Section, said wires lying freel in contact with the inner faces ofsa d long'l- "1 0 tu linal frame members in order to support In witness whereof I have hereunto set my sard gas conta-mers in the spacesbetween hand in the presence of two wltnesses.

sa1d transyerse frame members, 11ft wlres EWEN HENDERSON MITCHELL extendmg 1nter10r1y from the upper part of the structure to the lower part thereof, and W1tnesses:

- an outer cover extending exteriorly over the THOMAS W. Rooms,

rigid framework. WILLIAM A. MARSHALL. 

